Photosensitive compositions are known which are useful in many ways. These compositions in dry film form are particularly effective in the formation of photoresists for the preparation of printed circuits, and in photoimaging systems such as those containing photoxidizable leuco dyes. A basic problem with almost all types of photosensitive compositions is that when they are subjected to elevated temperatures they become thermally unstable within a short time period. In addition, many of the reactions known to be included within the term "thermal instability" proceed as well at room temperature, albeit more slowly than at elevated temperatures, and thus contribute to a shortened shelf life. To improve thermal stability numerous types of thermal inhibitors have been added to photosensitive compositions. While many of the thermal inhibitors have been adequate, care must be used in selecting inhibitors because the inhibitors may detrimentally affect other properties of the particular compositions in which they may be present. The properties which should not be affected include photosensitivity and printout image stability. Inhibitors such as hydroquinone, p-methoxyphenol, p-quinone, etc., although they are effective in preventing polymerization of ethylenically unsaturated monomers when present in photosensitive materials, they do not stabilize the printout image and may impair the photosensitivity of the materials.
It is desirable that photosensitive formulations be prepared containing compounds that provide thermal stabilization of the printout image without detrimentally affecting photosensitivity as well as other properties.